Aldol condensation is a vital tool in organic synthesis to create carbon-carbon bond between two aldehyde or ketone molecules. The aldol product (β-hydroxyaldehyde or β-hydroxyketone) possesses hydroxyl and carbonyl functional groups, enabling its conversion via successive reactions to numerous industrially important products such as diols, α,β-unsaturated aldehydes, α,β-unsaturated ketones, saturated alcohols, allylic alcohols, aldehydes, and ketones. However, the aldol condensation is a reversible process, a feature that limits the utility of this reaction in term of conversion, especially when the starting material is a ketone because of un-favourable equilibrium. Acetone condensation is an example for the synthesis of highly important products such as methyl isobutyl ketone (MIBK), diisobutyl ketone (DIBK), phorone (PH), and α-isophorone (IPH) with low acetone conversion and low selectivity for the desired product.
MIBK is an important product derived from acetone. It is used as a solvent in paint and protective coating systems. MIBK is commercially produced using a three-step process. The main reaction pathways for the synthesis of MIBK from acetone are shown in FIG. 1. The first step is the aldol addition of acetone to diacetone alcohol (DA, 4-hydroxy-4-methyl-2-pentanone). The second step is the aldol condensation of DA to mesityl oxide (MO, 4-methyl-3-penten-2-one). The final step is the selective hydrogenation of the carbon-carbon olefinic bond of MO to form MIBK. The most commonly observed side reactions are over-condensation and unselective hydrogenations.
Numerous catalysts are currently used in gas or liquid phase production of MIBK to obtain high yield with little success. The atmosphere, temperature and reaction phase play a vital role in the final yield of the MIBK.
The production processes are complicated and operational costs are high. The use of homogeneous liquid base and acid catalysts create a corrosive environment, require an additional neutralization process for their disposal, and generate a significant wastewater stream. Furthermore, the separation of DA and MO is mandatory for carrying out its successive step. Thus, there is a need for a better catalyst, which can be used in gas-phase production as well as in liquid phase production of MIBK. The MIBK production should provide a higher yield and, in turn, should become cost effective.